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timers: Get this_cpu once while clearing the idle state

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Calling smp_processor_id() on:
- In CONFIG_DEBUG_PREEMPT=y, if preemption/irq is disabled, then it does
not print any warning.
- In CONFIG_DEBUG_PREEMPT=n, it doesn't do anything apart from getting
__smp_processor_id

So with both CONFIG_DEBUG_PREEMPT=y/n, in preemption disabled section it is
better to cache the value. It saves a few cycles. Though tiny, repeated
adds up.

timer_clear_idle() is called with interrupts disabled. So cache the value
once.

Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Mukesh Kumar Chaurasiya (IBM) <mkchauras@gmail.com>
Link: https://patch.msgid.link/20260323193630.640311-5-sshegde@linux.ibm.com
This commit is contained in:
Shrikanth Hegde 2026-03-24 01:06:30 +05:30 committed by Thomas Gleixner
parent f6472b1793
commit 551e49beb1
1 changed files with 3 additions and 2 deletions
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5
kernel/time/timer.c
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@ -2319,6 +2319,7 @@ u64 timer_base_try_to_set_idle(unsigned long basej, u64 basem, bool *idle)
*/
void timer_clear_idle(void)
{
int this_cpu = smp_processor_id();
/*
* We do this unlocked. The worst outcome is a remote pinned timer
* enqueue sending a pointless IPI, but taking the lock would just
@ -2327,9 +2328,9 @@ void timer_clear_idle(void)
* path. Required for BASE_LOCAL only.
*/
__this_cpu_write(timer_bases[BASE_LOCAL].is_idle, false);
if (tick_nohz_full_cpu(smp_processor_id()))
if (tick_nohz_full_cpu(this_cpu))
__this_cpu_write(timer_bases[BASE_GLOBAL].is_idle, false);
trace_timer_base_idle(false, smp_processor_id());
trace_timer_base_idle(false, this_cpu);
/* Activate without holding the timer_base->lock */
tmigr_cpu_activate();